Analyze Customer Purchase Trends with Window Functions

An online retail company wants to analyze customer spending trends over months. Write a SQL query to calculate the total spending for each customer by month, along with the cumulative spending for each customer over time.

Requirements

Join the customers and orders tables on customer_id.
Group the results by customer and month of the order date.
Calculate total spending per customer per month.
Use a window function to calculate cumulative spending for each customer.

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique identifier for each customer
customer_name	VARCHAR(255)	Name of the customer

orders

Column	Type	Description
order_idPK	INT	Unique identifier for each order
customer_id	INT	Identifier linking to the customer who made the order
order_date	DATE	Date when the order was placed
amount	DECIMAL(10,2)	Total amount of the order

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